content: /*
   * Copyright 2011-2016 David Karnok
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package ix;
  
  import java.util.Iterator;
  
  final class IxDistinctUntilChanged<T, K> extends IxSource<T, T> {
  
      final IxFunction<? super T, K> keySelector;
  
      final IxPredicate2<? super K, ? super K> comparer;
  
      IxDistinctUntilChanged(Iterable<T> source, IxFunction<? super T, K> keySelector,
              IxPredicate2<? super K, ? super K> comparer) {
          super(source);
          this.keySelector = keySelector;
          this.comparer = comparer;
      }
  
      @Override
      public Iterator<T> iterator() {
          return new DistinctUntilChangedIterator<T, K>(source.iterator(), keySelector, comparer);
      }
  
      static final class DistinctUntilChangedIterator<T, K> extends IxSourceIterator<T, T> {
  
          final IxFunction<? super T, K> keySelector;
  
          final IxPredicate2<? super K, ? super K> comparer;
  
          K last;
  
          boolean once;
  
          DistinctUntilChangedIterator(Iterator<T> it, IxFunction<? super T, K> keySelector,
                  IxPredicate2<? super K, ? super K> comparer) {
              super(it);
              this.keySelector = keySelector;
              this.comparer = comparer;
          }
  
          @Override
          protected boolean moveNext() {
              Iterator<T> it = this.it;
  
              K prev = last;
              K curr;
  
              while (it.hasNext()) {
                  T v = it.next();
                  curr = keySelector.apply(v);
  
                  if (!once) {
                      once = true;
  
                      last = curr;
  
                      value = v;
                      hasValue = true;
                      return true;
                  }
  
                  if (!comparer.test(prev, curr)) {
                      last = curr;
  
                      value = v;
                      hasValue = true;
                      return true;
                  }
  
                  prev = curr;
              }
  
  
              done = true;
              return false;
          }
  
  
      }
  }
  